Telephone calls have been automatically routed through the Public Switching Telephone Network (PSTN) for as long as modern telephone switching equipment has existed. A telephone number corresponding to World Zone 1, which includes the United States, has a three digit Numbering Plan Area code (or NPA) and a three digit Exchange code (or NXX). Each NPA/NXX represents a telephone exchange. Further, each NPA/NXX combination is controlled by an operating company, designated by an Operating Company Number (OCN).
Telephone calls originating (calling party) and terminating (called party) in telephone exchanges controlled by different operating companies are routed between operating companies. Interexchange carriers, such as long distance companies, carry communications traffic between the telephone exchanges. In the past, communications traffic consisted of voice traffic that was transmitted in analog form. More recently, communications traffic has expanded to encompass voice and data traffic that are transmitted in digital form, such as in one or more data packets.
In order to create wireline regulation, the United States and Canada were divided into Local Access and Transport Areas (LATAs). A LATA corresponds to a geographical region in which a divested Regional Bell Operating Company (RBOC) is permitted to offer exchange telecommunications and exchange access services. The interexchange carriers provide routes between LATAs. Further, Telcordia Technologies publishes the Local Exchange Routing Guide (LERG), which is a monthly guide used to determine the routing of telecommunications services between LATAs. Therefore, interexchange carriers can access the LERG to determine one or more call routing options.
The rates charged by the interexchange carriers were previously determined through contract negotiations and were typically valid for an extended period of time. Generally, once an agreement with an interexchange carrier was reached, the interexchange carrier exclusively performed call routing between one or more originating and terminating points. Alternatively, a particular interexchange carrier could be designated as the carrier for all of a subscriber's long distance telephone calls. The rates applied to interexchange routing did not change frequently, as accurate billing depended on being able to determine the applicable rate for a particular call routed through an interexchange carrier.
With the wide-spread adoption of mobile communications, however, competition between interexchange carriers increased. Service providers were able to develop routing tables that compared the rates charged by various interexchange carriers. Further, service providers could make routing decisions based on the rates charged by the interexchange carriers. Because the rates were provided and entered into the routing tables manually, however, the rates associated with an interexchange carrier were only modified periodically.